DFG Priority Program SPP 1164
Nano- & Microfluidics:
Bridging the Gap between
Molecular Motion and Continuum Flow
Slippage and Nanorheololgy of Simple and Complex Fluids in Confinement
| Project Leader: | Prof. Dr. Karin Jacobs Universität des Saarlandes Fachrichtung 7.2 - Experimentalphysik Saarbrücken |
Summary
The properties of a confined liquids are very important for
applications involving e.g. flow through porous media or in
lab-on-a-chip devices. Solving the hydrodynamic equations for a liquid
flowing over a solid surface, one usually assumes the relative velocity
between liquid and solid to be zero. This is the so-called
“non-slip boundary condition”. Experiments with complex
fluids and, very recently, also with simple (Newtonian) Fluids have
shown that there can indeed be a non-zero velocity
(“slippage”) at the boundary. In the project we will study
experimentally why under which conditions this can take place. The
sizes involved are expected to be on the nm-scale.
On the same scale we will therefore determine the velocity and the shape of a moving liquid front. Both are known to serve as extremely sensitive “nano-rheometers” and give quantitative values for the viscosity and the slip length. It is expected from theory that slippage is enforced for smooth and low surface-energy substrates. In our experiments, we will vary these system properties and also properties of the liquid like viscosity and viscoelasticity. Since slippage can enhance the flow rate also on a macro-scale, slippage is an important issue in the design of microfluidic devices such as mixers etc. The vision is thus to gain a comprehensive picture on the nature of slippage, to find a molecular explanation for variable slip lengths in order to finally be capable to tailor surfaces in their ability to enhance slippage.
On the same scale we will therefore determine the velocity and the shape of a moving liquid front. Both are known to serve as extremely sensitive “nano-rheometers” and give quantitative values for the viscosity and the slip length. It is expected from theory that slippage is enforced for smooth and low surface-energy substrates. In our experiments, we will vary these system properties and also properties of the liquid like viscosity and viscoelasticity. Since slippage can enhance the flow rate also on a macro-scale, slippage is an important issue in the design of microfluidic devices such as mixers etc. The vision is thus to gain a comprehensive picture on the nature of slippage, to find a molecular explanation for variable slip lengths in order to finally be capable to tailor surfaces in their ability to enhance slippage.
Publications
- Dynamics in Thin Films: Interfacial Forces
R. Seemann, S. Herminghaus, K. Jacobs
Eds. S. Kalliadasis and U Thiele, Reihe CISM Courses and Lectures No. 490, Springer Wien New York,
ISBN 978-3-211-69807-5 (2007). - Slippage of Newtonian Liquids: Influence on the Dynamics of Dewetting Thin Films
R. Fetzer and K. Jacobs
Langmuir (in print) - Thermal Noise Influences Fluid Flow in Thin Films during Spinodal Dewetting
R. Fetzer, M. Rauscher, R. Seemann, K. Jacobs, and K. Mecke
Phys. Rev. Lett. 99 (2007) 114503 - Slip-controlled thin-film
dynamics
R. Fetzer, M. Rauscher, A. Münch, B. A. Wagner and K. Jacobs
Europhys. Lett. 75 (2006) 638 - New Slip Regimes and the
Shape of Dewetting Thin Liquid Films
R. Fetzer, K. Jacobs, A. Münch, B. Wagner and T. P. Witelski
Phys. Rev. Lett. 95 (2005) 127801 - Dynamics and structure formation in
thin polymer melt films
R. Seemann, S. Herminghaus, C. Neto, S. Schlagowski, D. Podzimek, R. Konrad, H. Mantz and K. Jacobs
J. Phys.: Condens. Matter 17 (2005) S267 - Trendbericht Mikrofluidik
K. Jacobs, R. Seemann and H. Kuhlmann
Nachrichten aus der Chemie 53 (2005) 300